An airbag for an occupant's leg restraint device includes an airbag that inflates in front of legs of an occupant in a front seat (a driver seat or a passenger seat) to restrain the legs of the occupant at an automobile collision. The airbag includes a first panel on the occupant side and a second panel on the instrument panel side that are sewn together. PTLs 1 to 3 disclose an airbag in which a first panel and a second panel are connected by tethers made of fabric to limit the inflated thickness of the airbag.
In the airbag of PTLs 1 to 3, the tethers extend in the lateral direction of the vehicle body (hereinafter simply referred to as “lateral direction”), and a chamber that is continuous from the left end side to the right end side of the airbag is formed in the uppermost part of the airbag.
PTL 1: Japanese Unexamined Patent Application Publication No. 2002-337642
PTL 2: Japanese Unexamined Patent Application Publication No. 2003-182504
PTL 3: Japanese Unexamined Patent Application Publication No. 2005-29102